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Marine Works

In connecting fenders to pier structures, should single lock nuts or double lock nuts be used?

In many pier structures the connection of fenders to piers is achieved by using single lock nuts. However, they do not perform well because some timber fenders loosen more easily when subject to vibrating loads due to berthing, wave and tidal actions. To solve this problem, double lock nuts should be adopted as they prove to function satisfactory in other structural elements which are subject to frequent vibration loads.

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What is the difference between weight chain, shear chain and tension chain in fender system?

The weight chain is used to sustain the weight of face and frontal panel. Shear chain help protect the fender from damage while the fender is in shear deformation and they are orientated at 20 – 30° to the horizontal. Tension chain serves to guard the fender against damage when the fender is under compression.

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What is the difference in application of surface-protecting fenders and energy-absorbing fenders?

Surface-protecting fenders are fenders that induce high reaction forces to berthing structures for the energy absorbed while energy-absorbing fenders are fenders which transmit low impact to berthing structures for the energy absorbed (Carl A. Thoresen (1988)).

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What is heeling during vessel berthing?

When a vessel berths on a fender system at a pier, the point of contact of the berthing ship may be above or below the centre of gravity of the ship. During the berthing operation, some kinetic energy is dissipated in work done to heel the ship i.e. the work done to bring the ship an angle of heel.

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Why is sulphate-resisting cement not used in marine concrete?

The main components of Portland cement are tricalcium silicate, dicalcium silicate, tricalcium aluminate and tetracalcium aluminoferrite. In sulphate-resisting cement, it contains a low amount of tricalcium aluminate in order to avoid sulphate attack. Otherwise, tricalcium aluminate would react with sulphates to form calcium sulphoaluminate and gypsum that cause expansion and crack the concrete structure.

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